We Don't Need the GPL Anymore
But if they then want to implement the new enhanced features added to the closed source version, then they do have to reinvent the wheel again.
Yes, they do. However, the features might give them new ideas for developing the open source version. The attribution mentioned by the earlier poster might attract additional developers to the project. It might help their personal professional lives to have their names on this product as well. These aren't the world's largest benefits, sure, but I think we're operating under different assumptions. I believe, and forgive me if I'm mistaken, you're assuming that if it was licensed under the GPL, the work would've been done and the changes returned. I'm assuming that if it wasn't under the BSD license, they wouldn't have done the work in the first place.